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4.
GAUGE INSTALLATION
4.1 ADJUSTING THE GAUGE WIRE TENSION
WARNING! Under no circumstances should the gauge tension be adjusted
after the gauge has been welded down.
Gauges are supplied with an initial reading of approximately 2500 microstrains.
This gives a range of ±1500 microstrains. This range is usually adequate for
most purposes and should not be altered except in unusual circumstances.
If the strain directions are known, the wire tension can be adjusted for greater
range in either compression or tension by completing the following:
1.
Attach the red and black leads to a readout box which has been set to
position E.
2.
Keep the gauge still by grasping the 4100 gauge by the tube, or the 4150
series gauges by the coil assembly.
3.
Using a mini wrench, rotate the tensioning nut. The position of the nut
controls the spring tension. To increase the range of measurement to
accommodate more compressive strain, turn the nut in a clockwise
direction and set the initial reading to between 2500 and 3000 microstrains.
To increase the range of measurement for tensile strains rotate the nut in a
counterclockwise direction, setting the initial reading to between 1500 and
2000. A rotation of 1/2 turn will give a change of about 600 microstrains.
Table 1 details various tension settings.
Setting Range
Microstrain Reading
Midrange
2500
Tension (67% of range)
2000
Compression (67% of range)
3000
TABLE 1: Guide to Initial Tension Settings
4.
The gauge end piece will often turn with the tensioning nut. After the
adjustment is made the end piece should be rotated back to its original
position so that the flats of the two end pieces are aligned. Again, hold the
tube/coil assembly while doing this.
5.
Check the reading. If okay, apply a drop of thread locking cement to
preserve the nut position and the tension.
4.2 INSTALLING THE 4100/4150 VIA SPOT WELDING
CAUTION! Wear safety glasses while performing the following tasks.
4.2.1 PREPARE THE SURFACE
The surface of the steel member should be flat, clean, and free from rust, grease,
and pitting. Degrease the surface using an appropriate cleaning agent, then use
a power grinder or sander, file, wire brush or sandpaper, to achieve a flat,
smooth surface.
4.2.2 SPOT WELD TEST STRIPS
Before welding, it is necessary to test the spot welder to make sure that the
correct weld energy is being used. Weld energy, and to a certain extent, contact
pressure, determines the quality of the weld. Approximately 20 to 40 watt-
seconds of weld energy is required to properly weld 4100 or 4150 strain gauges
to structural steel.
MODEL 4100/4150 SERIES VIBRATING WIRE STRAIN GAUGES | GAUGE INSTALLATION | 9
Available Microstrain Range
Tension
Compression
1500
1500
2000
1000
1000
2000
1:
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